The present invention is directed to a circuit arrangement for generating a constant output voltage.
German reference DE-A1 92 114 237 discloses such a circuit arrangement. This publication discloses an arrangement having two identical frequency converters that feed a common load via decoupling diodes. Each of the two frequency converters is in the position to supply the load by itself. The frequency converter respectively comprises a regulator for regulating the output voltage to a constant value. The voltage regulator works in the sense that the deviation of an actual value voltage output by an arrangement for forming actual values from a reference voltage is optimally minimized. A voltage divider with whose assistance the actual value of the output voltage is acquired lies at the common load.
In order, given high precision of the output voltage, to prevent voltages that appear at the user and are applied to the user in some other way from initiating the regulator to inhibit the circuit arrangement, a reference potential terminal of the regulator lies at the one side of the decoupling diode and the voltage divider lies at the other side of the decoupling diode. An integrated circuit that, with reference to its reference potential terminal, processes positive actual value voltages serves as regulator. The positive pole of the output of the circuit arrangement lies at reference potential.
On the other hand, the arrangement for mixed value formation can be fashioned such that the actual value for the regulator is formed as a mixed value of the voltage preceding and following the decoupling diode. When a low tolerance of the output voltage is required, then the part of the voltage following the decoupling diode must predominate. In this case, however, the current supply device that is activated first inhibits the other. If the mixing ratio of the measured values is preselected in order to avoid this problem and is only 1:1 following the decoupling diode, then only a limited precision of the user voltage can be achieved, since the voltage drop-off at the decoupling diode is highly dependent on the temperature and on the load current.